PPRuNe Forums - View Single Post - When practicing vortex ring.........
View Single Post
Old 29th June 2012 | 15:21
  #25 (permalink)  
[email protected]
25 Anniversary
 
Joined: Apr 2000
: ATP+Mil
Posts: 10,959
Likes: 1,814
From: EGDC
HF - I believe what I have stated is what the OP was questioning so maybe his terminology caused confusion.

If you are in a 2000' hover over the ground and the wind is blowing from behind you, are you downwind or do you have negative airspeed? The aircraft will handle the same and you are still further from a safe speed to avoid VRS than if you were hovering into wind/with positive airspeed.

However, meteorologists refer to system relative wind to explain the formation of warm and cold conveyor belts so the term wind can be used in a non-earth frame of reference

TeT - if the root and inboard section of the blade is stalled and the outboard section and tip are immersed in recirculating vortices then there isn't much of the disc left to produce rotor thrust to oppose weight - that is full VRS. If you raise the lever, you exacerbate the problem as the increase in rotor drag can exceed the rotor torque and Nr will decrease. The helo won't accelerate indefinitely but it will fall faster - if you don't have enough time/height to recover you are stuffed.

Theoretically, if you have a powerful enough helo you can pull through VRS but the best option is to lower the lever to achieve the windmill brake state or autorotation.

Last edited by [email protected]; 29th June 2012 at 15:27.
crab@SAAvn.co.uk is offline  
Reply